After you have selected the contacts within a segment, you may want to remove some of them. You can do this by manually removing them from the lines in the Segment window, but it is easier and faster to use the Remove Contacts, Reduce function.
You can use the Remove Contact, Reduce function when you would like to specify the contacts you want to remove from the segment. To specify which of the contacts you would like to keep, use the Remove Contacts, Refine function.
Open the 
Segment window.
Find the segment you want to reduce, and click Function, Segment, Remove Contacts, Reduce. The Remove Contacts - Reduce window appears.
On the Contact tab, in the Field field, select one or more fields to specify the information that you want to use to select the contacts to be removed from the segment.
In the Filter field, apply a filter to these fields.
On each of the remaining tabs, repeat steps 3 and 4 to enter one or more additional filters.
Click OK.
You can reduce a segment as many times as you want. Click Functions, Segment, Go Back function, if you have reduced the segment by mistake and want to go one step back.
If you are not familiar with the Remove Contacts, Reduce function, you may want to use the Segment wizard to reduce your segments.
After you have selected all the contacts to be included in your segments, you may want to save the segmentation criteria. You can then use these criteria to create new segments.
You can see a list of the segment criteria that you have used by
clicking the AssistButton 
to the right of the No. of Criteria Actions field.